Mold for molding link chains of plastic material



Jan. 20, 1970 MOLD FOR MOLDING LINK CHAINS OF PLASTIC IJKATERIAL FiledSept.

J. FUNKE 2 Sheets-$heet 1 INVENTOR JUHANNES FUNKE Jan. 20, 1970 J. FUNKE3,490,109

MOLD FOR MOLDING LINK CHAINS OF PLASTIC MATERIAL Filed Sept. 5, 1967 2Sheets-Sheet 2 INVENTOR JUHANNES FUN KE United States Patent US. C].18-42 9 Claims ABSTRACT OF THE DISCLOSURE A mold for producing chainsections of plastic material with jointless links which mold permitssimultaneous molding of chain sections of odd-numbered links even ofcircular cross-section of the links. Heretofore, difficulties wereencountered, even when using four-part molds, to remove such moldedchain sections from the mold because the undercuts made its openingimpossible. When guiding two juxtaposed parts of said four mold parts,said two parts being freely movable towards and away from each other,with free play in guiding means under an acute angle, for instance, of80, with respect to the vertical central lane of the mold so as toengage the other two mold parts which are also freely movable towardsand away from each other, and thereby to close the mold, the moldedchain section can readily be removed on opening the mold. While thefirst two parts of the mold are joined to each other and are separatedfrom each other by said guiding means, the other two parts of the moldare, for instance, pulled apart from each other by means of returnsprings.

The plastic material is injected into the mold through a channel whichbranches out crosswise into four channels of which two are connected tothe cavities forming the middle link and the other two to the cavitiesforming the end part on each link adjoining the middle link and, if afive-link chain section is molded, the cavity forming the middle link isconnected at its ends with the cavities forming the terminal links ofthe chain section.

By further increasing the number of supply channels accordingly, anyodd-numbered ling chain section can be molded.

BACKGROUND OF THE INVENTION The present invention relates to a mold forplastics and more particularly to an injection mold for producing chainsof plastic materials or synthetic resins with weldless or jointlesslinks of substantially circular cross-section, and to a process ofproducing such chains.

It is known to use molds having a split, four-part matrix with twojointing planes or faces which are arranged vertically to each other andwhich pass through the central planes of adjoining links. Such molds areused, for instance, to insert by injection molding weldlessly orjointlessly a single chain link into two prefabricated links positioneduprightly and edgewise in said mold. Thereby, the one jointing plane orface is arranged in the central plane of the link to be inserted whilethe other jointing plane or face is provided in the central planes ofthe prefabricated links which have been placed in corresponding recessesof the mold. When molding by injection a single link, there are nodifficulties encountered provided the total height of the mold at theplace of the recesses for the prefabricated links is dimensioned in sucha manner that the split matrix, i.e. the four parts of the mold can bemoved, on opening the mold with the chain links inserted therein, by atleast half the thickness of the chain links in vertical direction to thejointing plane or face.

3,490,100 Patented Jan. 20, 1970 "ice It is also known to produce byinjection molding five links simultaneously. However, due to thedifficulties encountered in removing the molded links from the mold,this process was applicable only to molding links with a flat,rectangular, or the like cross-section. Otherwise it was not possible toopen the mold.

SUMMARY OF THE INVENTION It is one object of the present invention toprovide an injection mold which enables simultaneously molding more thanone chain link, for instance, three or five, or even more, chain linksof any cross-section and even of circular cross-section withoutdifficulty, thus increasing the mold output considerably.

Other objects of the present invention and advantageous features thereofwill become apparent as the description proceeds.

As stated above, when attempting simultaneously molding more than onechain link, the difficulty is encountered that the four parts of themold cannot be taken apart and disassembled if the cross-section of thelinks is circular or nearly circular. This is due to the undercuts whichmake such disassembling theoretically impossible.

This difiiculty is overcome by the present invention by guiding at leasttwo juxtaposed parts of the mold by means of guiding means which arearranged in an acute angle to the central plane of the link enclosed bysaid parts. Even then, however, it is an essential feature of thisinvention that the guiding means are provided with a certain amount offree play or slackness. Surprisingly it has been found that thetheoretically unsolvable problem of disassembling the mold parts can besolved only by causing firm and reliable assembly and closing of themold parts, on the one hand, but by providing a certain free play orslackness in the sloping or slanting guiding means after a short liftingmovement. A third essential feature of this invention is that the chainlinks remain deformable to a slight extent shortly after molding and,therefore, yield slightly. Experience has shown, that the chain linkscan be removed in this manner from the mold without difficulty and thattheir circular cross-section remains competely unaffected.

BRIEF DESCRIPTION OF DRAWINGS In order that the invention may be moreclearly understood, reference will now be made to the accompanyingdrawings which show some embodiments thereof by way of example. In saiddrawings FIG. 1 is a cross-sectional view of a mold according to thepresent invention while in open condition;

FIG. 2 is a cross-sectional view of the same mold in closed condition;

FIG. 3 is a sectional view through the mold according to FIG. 2 alongthe line III-III;

FIG. 4 is a sectional veiw through said mold of FIG. 2 along the lineIV-IV; and

FIG. 5 is a schematic view of a chain with five links molded in a moldaccording to the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT Referring now to thedrawings, the mold according to this invention as illustrated in FIGS. 1and 2 comprises stationary, fixed upper platen 10 with two lateralguiding blocks 11 and 12 provided with guide means such as recesses orgrooves 13 and 14. Said guiding means 13 and 14 are arranged so thatthey form, for instance, an angle of about with respect to the verticalcentral plane 15 of the mold. Two mold parts 16 and 17 forming thematrix are guided in said guiding means 13 and 14. Said parts 16 and 17can be moved upwardly in the direction of arrow 19 by means of plunger18. Thereby they are also moved horizontally towards each other untilthey contact each other as shown in FIG. 2. They are provided withupwardly directed projections or shoulders 20' and 21 withcounter-guiding planes or surfaces 22 and 23. On moving upwardly, planes22 and 23 of mold parts 16 and 17 are brought in contact withcorresponding guiding planes 24 and 25 of two upper mold parts 26 and 27serving as matrix which are movably arranged on basal plane or surface28 of upper platen 10 in such a manner that said mold parts 26 and 27can be moved horizontally and rectilineally towards each other. As shownin FIGS. 1 and 2, mold parts 16 and 17 have outer surfaces 16 and 17'which are slanted at about the same angle of inclination of 80 as theguiding means 13 and 14 of guiding blocks 11 and 12. Said mold parts 26and 27 are pulled apart from each other by return springs 29 and 30which are attached at their other ends to guide blocks 11 and 12 whenthe mold is opened. The four mold parts 16, 17, 26, and 27 are providedwith cavities shaped as shown in FIGS. 3 and 4 to receive the plasticmaterial for molding.

FIGS. 3 to show injection channel 31 which branches out at its bottominto channels 32 and 33 forming a cross being coordinated in space.Channels 32 lead in both directions to the central part of the cavity 34forming the legs or side parts 34' of link 35' arranged in the middle ofthe chain section of three or more links to be molded. Channels 33 leadto the cavities 36 forming the end parts 36' of adjoining links 37, saidend parts 36' facing each other. According to FIG. 5 the cavity 34forming the middle link 35' of the chain section to be molded thus issupplied with plastic material through two channels 32 while thecavities 37 forming the end of each of the adjoining links 37' aresupplied therewith through channels 33. It is an essential feature ofthe present invention that, in case five or more links are to be molded,a larger amount of plastic material must be supplied to the cavity 34forming middle link 34 because the cavities 38 forming links 38'positioned at the end of the chain section to be molded are connectedwith the cavity 34 forming said middle link 34' through channels 39. Thechain section obtained on molding in the above described manner has fiveinterconnected link members 34', 37', and 38' which are interconnectedby intermediate sprues 31' and 32' attached to middle link 34', sprues33' attached to links 37' adjoining middle link 34, and sprues 39connecting links 34' and 38'. These intermediate connecting pieces orsprues are subsequently removed from the molded chain section, forinstance, by nipping or cutting them oif.

Molding of chain sections of three or more links according to thepresent invention is eifected by first closing the mold by moving moldparts 16 and 17 upwardly whereby their faces or planes 22 and 23 engagethe faces or planes 24 and 25 of mold parts 26 and 27. At the same timemold parts 16 and 17 are guided by guiding blocks 11 and 12 and saidparts as well as parts 26 and 27 are moved towards each other to formthe mold. After the mold has been closed in this manner, the plasticmaterial is injected thereinto through channel 31 and forms link 34' bypassing through channels 32, links 37' by passing through channels 33,and links 38' by passing from link 34 through channel 39. After allowingthe plastic material to solidify, the mold is opened by movingdownwardly plunger 19 with mold parts 16 and 17 which are horizontallymovably atached thereto. On such downward movement mold parts 16 and 17are separated from each other by guiding means 13 and 14 in guidingblocks 11 and 12 while mold parts 26 and 27 are separated from eachother by return springs 29 and 30. The molded chain section can thenreadily be removed from the mold and the molding process can berepeated.

The mold as well as the process of this invention may, of course, besubject to modifications. Thus it is possible to produce chain sectionsof another cross-section than circular cross-section. The advantages ofthe mold as well as of the process according to the present inventionare obtained in all those cases in which the cross-section of the chainlinks shows undercuts which render it impossible to separate the fourparts of the mold from each other in the usual manner. The inside lengthof the links may also be varied because it is not necessary, as has beenrequired heretofore, to insert by injection molding a connecting linkinto the prefabricated links positioned edgewise uprightly in the mold.Thus it is possible to produce, according to the present invention, alsochain sections of links of a shorter inside length. It is also possibleto provide a mold, the cavity of which will produce chain sections inwhich only the terminal links have a larger inside length and which thuspermit to position them edgewise uprightly into the mold. Channels 31,32, 33, and 39 may also be arranged in a different manner. The angleunder which guiding means 13 and 14 are arranged with respect tovertical central plane 15 of the mold may differ from an angle ofprovided it is an acute angle with respect to said plane 15.

The plastic material used to make the chain links and chain sections maybe preberably polyamide polyethylene and other suitable plasticmaterials.

Of course, many other changes and variations may be made by thoseskilled in the art in accordance with the principles set forth hereinand in the claims annexed hereto.

I claim:

1. Mold for producing chain sections of plastic material havingjointless links, said mold comprising an upper platen, two guidingblocks firmly attached thereto, said guiding blocks having guidingmeans, said guiding means being arranged at an acute angle with respectto the central plane of the mold, four mold parts with two jointingplanes arranged vertically to each other and passing through the centralplanes of adjoining links, at least two of said mold parts beingjuxtaposed, said first two mold parts being guided with free play insaid guiding means under an acute angle with respect to said verticalcentral plane of the mold, said first two mold parts engaging the othermold parts to enclose the cavity of the mold, cavities provided in thefour mold parts, said cavities corresponding, when the mold is closed,to the link chain section to be molded, means for guiding said firstmold parts in said guiding means to engage and disengage the other moldparts and to open and close the mold, and means for supplying theplastic material to the mold cavity.

2. The mold according to claim 1, wherein the acute angle at which theguiding means guide the juxtaposed first mold parts with respect to thevertical central plane of the mold is an angle of about 80 3. The moldaccording to claim 1, wherein the other two mold parts are arranged soas to be vertically removable from the vertical central plane of themold.

4. The mold according to claim 1, wherein return springs are attached tosaid two other mold parts, the opposite ends of said return springsbeing fastened to said guiding blocks, said return springs separatingand pulling said other two mold parts away from each other on openingthe mold.

5. The mold according to claim 1, wherein said two first mold parts areprovided with counter-guiding means inclined inversely to said guidingmeans so as to cause movement of the other two mold parts towards eachother to close the mold.

6. The mold according to claim 5, wherein the counterguiding means areshaped as counter-guiding planes engaging and enclosing the other twomold parts.

7. The mold according to claim 1, wherein the cavities corresponding tothe link chain sections, when the mold is closed, are cavities formolding a link chain section of three links and wherein an injectionchannel is provided vertically to the center of the middle link of thechain section to be molded, said injection channel branching out intoconnecting channels forming a cross being coordinated in space, two ofthe branches of said cross of connecting channels being connected to thecavities forming the legs of said middle link and each of the other twobranches being connected to the cavities forming the end parts of eachof the links adjoining the middle link.

8. The mold according to claim 1, wherein the cavities corresponding tothe link chain sections, when the mold is closed, are cavities formolding a link chain section of five links, wherein an injection channelis provided vertically to the center of the middle link of the chainsection to be molded, said injection channel branching out intoconnecting channels forming a cross being coordinated in space, two ofthe branches of said cross of connecting channels being connected to thecavities forming the legs of said middle link and each of the other twobranches being connected to the cavities forming the end parts of eachof the links adjoining the middle link, and wherein connecting channelsare provided connecting the cavities forming the end parts of each ofthe links following said links adjoining the mddle link with thecavities forming the end parts of said middle link.

9. Mold for producing chain sections of plastic material havingjointless links, said mold comprising an upper platen, two guidingblocks firmly attached thereto, said guiding blocks having guidingmeans, said guiding means being arranged at an acute angle with respectto the central plane of the mold, four mold parts with two jointingplanes arranged vertically to each other and passing through the centralplanes of adjoining links, at least two of said mold parts beigjuxtaposed, said first two mold parts being guided with free play insaid guiding means under an acute angle with respect to said verticalcentral plane of the mold, said first two mold parts being provided withcounter-guiding means inclines inversely to said guiding means, saidcounter-guiding means engaging and enclosing the other two mold parts toenclose the cavity of the mold formed by said four mold parts on guidingthe first two mold parts in said guiding means, said other two moldparts being separable from each other, on opening the mold, by springmeans, the one end of said spring means being attached to said other twomold parts and the other end to said guiding blocks, cavities providedin the four mold parts, said cavities corresponding, when the mold isclosed, to the link chain section to be molded, means for guiding saidfirst mold parts in said guiding means to engage and disengage the othermold parts and to open and close the mold, and means for supplying theplastic material to the mold cavity.

References Cited UNITED STATES PATENTS 510,748 12/1893 While 249571,475,032 11/ 1923 Shrum et a1. 2,051,653 8/1936 Rich 249-57 2,891,2836/1959 Cramer et al. 3,092,916 9/ 1962 Campbell. 3,333,299 8/1967Florjancic. 3,373,460 3/ 1968 Ladney. 3,427,801 2/1969 McLeish 24957 XFOREIGN PATENTS 1,456,775 9/1966 France.

I. HOWARD FLINT, JR., Primary Examiner U.S. Cl. X.R. 24957

